The research program is developing among three lins: (1) Biochemical analyses of meiosis in rat spermatocytes; (2) Cytogenetic and fine structure studies of spermatogenesis in Drosophila; (3) Parthenogenesis in mice. Chromosomal proteins which appear to be involved in rat meiosis are being analyzed, special emphasis being given to a DNA binding protein that facilitates renaturation. The metabolism of DNA at the pachytene stage in relation to crossing over is being characterized in the expectation that a common mechanism for effecting crossing over in higher organisms will be found. Some initial studies have also been made on the relation between nuclear membrane metabolism and the meiotic pairing of chromosomes. Efforts to culture Drosophila spermatids through spermatogenesis are progressing, though not markedly. Efforts are primarily being spent on finding the right culture medium. Substantial progress is being made in the analysis of sperm morphology and survival in relation to genetically determined lesions in chromosome condensation during spermatid development. Initial studies of parthenogenesis in mice have concentrated on analyzing the mechanism of parthenogenesis and its inheritance in the LT/Sv mouse strain. Such analysis is essential to developing an experimental parthenogenetic system.